1. Field of the Invention
This invention relates to a connector for joining members of a same material of wood, laminated wood or stone, or for joining a member of wood or laminated wood with a member of stone or concrete, and more specifically relates to a connector used in furniture or wooden dwellings or for joining structural members with joints and couplings in constructions having frames in large stud partition constructions using heavy timbers.
2. Description of the Related Art
In recent years, connectors for joining beams and pole plates, pole plates and columns, girt and independent columns for reducing labor time in the construction of houses have been developed along with joints and couplings for streamlining the work process.
For instance, Japanese U.M. Laid-open No. Sho 63-162008 shows framing fixtures used for stud partition frame working methods, Japanese U.M. Laid-open No. Hei 2-93401 shows reinforcement fixtures for joints at the bottom ends of columns and the foundations in frame type stud partitions Japanese Patent Laid-open No. Hei 3-295946 shows protruding dowel fixtures and stud frame partitions in lower wall structures using the dowel fixtures, Japanese Patent Laid-open No. Hei 2-300442 shows connecting structures for wood type structure materials with a stud frame partition that is not dismantled after connection. These inventions all use metal fixtures, or nuts or bolts to connect the structural materials.
Additionally as joint structures, Japanese Patent Laid-open Nos. Sho 63-14939, 63-14940 and 63-14941 show joints providing improved structural strength in stud frame partitions.
However these conventional connectors and joints all require a large number of metal bolts, nuts and washers, making installation difficult during the work process. Another drawback is these metal parts are difficult to carry on the job because of their large size and weight and further represent a safety hazard in work done at locations high above ground.
Besides the extra work needed to correct mistakes in installation of fixtures, there is the drawback that installations embedded at specific positions drilled for placing of cylinders and plugs, and the threading of bolts in holes in the embedded cylinders and plugs is very troublesome work requiring a large amount of man-hours and delaying building construction schedules.
Wood pieces joined by items like bolts or nuts have the drawback of loss of mechanical strength since the wood material is prone to loose its tightness and become loose when the wood material contracts over the years. Further, along with the drop in durability occurring when the metal parts of fixtures oxidized from exposure to moisture, mechanical strength and durability also decreases from corrosion occurring in metal parts such as bolts and nuts in imported materials due to exposure of the packed lumber to salt during ocean transport.
Another problem is the melting of exterior connecting bolts and metal fixtures during fires, lowering mechanical strength and the danger resulting from the house walls collapsing during fires. The greatest defect inherent in frameworks of wood material is the weakness of the connecting portion. A variety of joints and couplings are available from old carpentry methods to maintain physical strength but these contrivances are all complicated and their machining requires more man-hours thus worsening productivity. Yet another problem is that large timber pieces are difficult to mass produce and troublesome to procure, also since the maximum span of wood or laminated wood arches or trusses is limited by road traffic regulations, these pieces could not be transported.
In view of the above, the inventor of this invention, in an earnest attempt to resolve the above-mentioned problems made a patent application in Japanese Patent Application No. Hei 4-164402 proposing a connector with a simple joint and coupling doing away with conventional complicated joints and couplings, and used with an adhesive agent to improve structural strength and simplify the joint, coupling or connection job operation while drastically reducing the required man-hours, along with a connecting method for a structural member excelling in productivity and reducing man-hours by simplification of the processing technology for the joint, coupling or connection that utilized the above proposed connector, and having the further advantage of a connection for a structural member providing high fire resistance and superior structural strength.
However while this invention is superior to conventional fixtures and installation methods in fire resistance, productivity, ease of installation and workability, a drawback still exists in that the connector is made of a single layer of metal or plastic, so that for instance when the connecting surface of the structural material is narrow, the specified strength cannot be obtained if a connector with small diameter is used.
On the other hand, even when the diameter of the connecting surface is large and great strength is not required, a connector heavier than needed is used causing disadvantages in efficiency and job workability.